1. Field of the Invention
The present invention relates to a wavelength conversion apparatus for generating harmonics using nonlinear optical crystals, and in particular, to shapes of the harmonic output facet of nonlinear optical crystals, and shapes of the harmonic output-window of cases for housing such crystals.
2. Description of the Related Art
A conventional wavelength conversion laser apparatus reduces reflection losses of harmonics at a nonlinear optical crystal facet by Brewster-cutting the harmonic output facet of the nonlinear optical crystal (for example, refer to Patent Document 1).
Patent Document 1: Specification of U.S. Pat. No. 5,850,407 (Section 4, FIG. 1-A and 1-B)
In a situation where a Brewster-cut nonlinear optical crystal is used as in a conventional wavelength conversion laser, problems have been that output directions of the harmonics are skewed with respect to the optical axis of light passing through the nonlinear optical crystal, and that positioning later-stage light guiding systems is difficult. Moreover, a problem with the nonlinear optical crystal has been that when the facet deteriorates due to the harmonics, or when output power of the harmonics is decreased due to deposition of impurities, etc., if the position of the nonlinear optical crystal is shifted, the optical axis of the harmonics deviates.